1. Field of the Invention
The present invention relates to wireless networks, and more particularly, to operation of wireless mobile devices during unavailability of wireless networks.
2. Description of the Related Art
Wireless networks are often used to transmit messages from one location in a network to a destination location in the network. These messages contain data to be supplied to the destination location. More specifically, the messages include a header portion and a data portion. The header portion includes an address of the destination location, and the data portion contains data. The destination location is, for example, a mobile device or a server. A mobile device typically interacts with wireless networks to receive various types of notifications or to request and receive data from another network to which the wireless network is connected.
FIG. 1 is a block diagram of a conventional wireless communication system 10. The wireless communication system 10 includes a server 12, a wireless network 14, and mobile devices 16. There are n mobile devices 16-1 through 16-n. The server 12 is typically a computer system that operates to send and receive messages to and from the mobile devices 16. The messages are often blocks of data that are to be transmitted to the mobile device 16. As examples, the data can pertain to various types of notifications, electronic mail, news data, configuration information, data files, library files, program files, etc. The messages can also be requests for information (e.g., certain data) that are transmitted from the mobile devices 16 to the server 12. The server 12 may also connect to other wired or wireless networks to receive messages from or forward messages to other computer systems. As an example, the server 12 can be connected to the Internet. For example, the server 12 can be a proxy server (or link server) coupled to the Internet or a network gateway coupled to a network. The tremendous growth of the Internet in recent years has fueled the need to provide mobile devices such as mobile telephones, personal digital assistants (PDAs) and the like with access to information and services available on the Internet.
The wireless network 14 typically uses radio transmissions to communicate with the mobile devices 16. The wireless network 14 can use a variety of different networks and communication protocols. Examples of wireless networks include Cellular Digital Packet Data (CDPD), Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA) to name a few, and each of these wireless networks has different data transfer characteristics such as latency, bandwidth, protocols and connection methods. As examples, protocols can be Internet Protocol (IP), Short Messaging System (SMS) and Unstructured Supplementary Service Data (USSD), and connection methods can include packet switched or circuit switched.
As an example, a message to be sent by the server 12 to the mobile device 16-2 would contain an address that particularly identifies the mobile device 16-2. The message is then provided by the server 12 to the wireless network 14. For example, one wireless data network is a packet switched network using a Small Message Server Center (SMSC) which has a relatively small packet size (e.g., 140 bytes). The wireless network 14 causes the message to be properly routed to the mobile device 16-2 (i.e., in accordance with the address). The transmission between the wireless network 14 and mobile device 16-2 is wireless. The mobile device 16-2 receives the message that has been transmitted to the wireless network 14. The mobile device 16-2 can then store the message and perform predetermined processing actions such as, for example, notifying a user of the mobile device 16-2 of the reception of the message.
In some wireless networks, the server and the mobile devices can be connected by two or more channels. In one case, the server and mobile devices can be connected over a one-way data channel and a two-way data channel. A representative network (e.g., GSM) having such characteristics can use a Short Message Service Center (SMSC) to provide the one-way data channel and an Interworking Function (IFW) to provide the two-way data channel. In such a network, the one-way data channel is often considered a narrowband channel and the two-way data channel is often considered a wideband channel. As an example, the narrowband channel can transfer data at a rate of about 400 bits per second (bps), while the wideband channel can transfer data at a rate of at least 14400 bps. It is thus not uncommon that a server and a mobile device be connected (or connectable) by both a two-way channel and a one-way channel. Typically, the server and the client will decide to use either or both of the channels depending on the urgency of the data, the cost willing to incur, etc. Use of a two-way channel often causes the mobile device to incur charges (i.e., fees) from a carrier that provides the service to the mobile device. In contrast, use of a one-way, narrowband channel is often available at no cost or at a fixed cost regardless of usage.
One problem with the conventional wireless communication systems is that the operation of mobile devices are very much dependent on availability of their wireless network. In other words, when the wireless network is unavailable, the mobile devices may stop processing user inputs as they wait for a response from a remote server via the wireless network. Unavailability of a wireless network can result from a user of a mobile device exceeding their geographic range of coverage. Unavailability also effectively results from a wireless network having high latencies or a wireless network having sporadic connectivity. Because of the dependency of the operation of mobile devices on the availability of wireless networks, mobile devices often have to wait for resources from a remote server.
Mobile devices are often provided with cache memories that temporarily store previously requested and obtained resources from remote servers. A cache memory is helpful in reducing the dependency of mobile devices on network availability. However, the cache memory is only helpful when the newly requested resource happens to reside in the cache memory. Hence, if the newly requested resource was not previously requested, then the newly requested resource would not be stored in the cache memory. Also, even it the newly requested resource were at one point in time stored in the cache memory, a reclamation or clean-up algorithm could have removed it from the cache memory to provide space for newer requested resources.
Another problem with the conventional wireless communication systems is that the dominating application model has a synchronous nature. The synchronous nature causes the application to wait for responses to requests to remote servers (unless satisfied by the cache memory). The wait times are unacceptably long when the wireless network is unavailable to the mobile devices.
One popular application is a network browser that is used on mobile devices to browse a network such as the Internet. Such as network browser is known as a web browser. The network browser is often requesting resources from remote servers over the wireless network. Hence, network browsers are particularly sensitive to network unavailability (e.g., due to out of coverage, high latencies, or sporadic connectivity). Consequently, it is common for network unavailability to induce significant waits for the users of network browsers on mobile devices.
Thus, there is a need for techniques to reduce delays faced by users of mobile devices due to unavailability of wireless networks.
Broadly speaking, the invention relates to improved techniques for reducing delays faced by users of mobile devices due to unavailability of wireless networks. The invention has at least three aspects that facilitate the reduction of delays faced by users of mobile devices during unavailability of wireless networks. A first aspect of the invention allows mobile devices to communicate with remote servers using asynchronous communications, namely device to continue while the asynchronous request is processed in the background. A second aspect of the invention pertains to the use of content channels with mobile devices. The content channels are stored and retained in cache memory so that their resources are guaranteed to be locally available, regardless of availability of wireless networks. A third aspect of the invention pertains to improved list processing within mobile devices such that lists can be manipulated without server interaction. These various aspects of the invention can be used separately or in combination.
The invention can be implemented in numerous ways, including as a method, a computer readable medium, an apparatus, and a system. Several embodiments of the invention are discussed below.
As a method for sending a resource request of a mobile device to a remote server through a wireless network, an embodiment of the invention includes the acts of: receiving a resource request, the requested resource being associated with the remote server; determining whether the requested resource is of a synchronous type resource request or of a an asynchronous type resource request; placing the resource request in an outgoing queue and not awaiting a resource reply when the resource request is determined to be an asynchronous type resource request; and when the resource request is determined to be a synchronous type resource request, performing the acts of (i) determining whether the requested resource is present in a local cache memory of the mobile device; (ii) supplying the requested resource from the local cache memory when it is determined that the requested resource is present in the local cache memory; and (iii) sending the resource request to the remote server through the wireless network and awaiting a resource reply when it is determined that the requested resource is not present in the local cache memory.
As a mobile device that connects to a remote server through a network, an embodiment of the invention includes: an application that executes on the mobile device, the application produces outgoing messages that are to be sent to the remote server; an asynchronous message queue that stores outgoing messages from the application that are to be sent from the mobile device to the remote server; and an asynchronous message manager that manages the sending of the outgoing messages from the asynchronous message queue to the remote server through the network.
Optionally, the mobile device can further include a cache memory that stores resources likely to be requested by the application, a channel manager that loads a content channel into the cache memory from the remote server through the wireless network, and a list manager that manages lists provided on the mobile device such that lists can be manipulated without interaction with the remote server through the network.
As a method for storing a content channel from a remote server onto a mobile device through a wireless network, the content channel including resources, an embodiment of the invention includes the acts of: receiving an instruction to load the content channel into a cache memory of the mobile device; determining whether the content channel can fit within a reserved portion of the cache memory of the mobile device; and loading the content channel into the reserved portion of the cache memory from the remote server through the wireless network when the determining determines that the content channel is able to fit within the reserved portion of the cache memory.
As a method for manipulating a list resident on a mobile device used with a wireless communication system, an embodiment of the invention comprising the acts of: displaying a list on a display device of the mobile device, the list being displayed from a descriptive file; receiving, at the mobile device, a list command to modify the displayed list; locating a list object stored within the mobile device, the list object corresponding to the displayed list; modifying the list object in accordance with the list command; obtaining, from the list object, a pointer to the descriptive file; locating a portion of the descriptive file to be modified using at least the pointer; and modifying the located portion of the descriptive file in accordance with the list command.
As a computer readable medium including computer program code for sending a resource request of a mobile device to a remote server through a wireless network, an embodiment of the invention includes: computer program code for receiving a resource request, the requested resource being associated with the remote server; computer program code for determining whether the requested resource is of a synchronous type resource request or of a an asynchronous type resource request; computer program code for placing the resource request in an outgoing queue and not awaiting a resource reply when the resource request is an asynchronous type resource request; and computer program code for sending the resource request to the remote server through the wireless network and awaiting a resource reply when the resource request is a synchronous type resource request.
The advantages of the invention are numerous. Several advantages that embodiments of the invention may include are as follows. One advantage of the invention is that operation of mobile devices is less dependent on network availability. As a result, users of mobile devices experience better responsiveness and less waiting. Another advantage of the invention is that both synchronous and asynchronous messaging are available to mobile devices. Still another advantage of the invention is that a programmer or content author can determine how navigation is performed, namely whether synchronous requests or asynchronous requests are used. Yet another advantage of the invention is that lists can be manipulated on mobile devices without having to support or provide the significant amounts of resources needed to provide scripting. Another advantage of the invention is the ability to obtain and guarantee the presence of certain content channels at mobile devices.